1. Field of the Invention
The present invention relates to polyphenylene ether copolymers (PPE copolymers),preparation thereof, and resin composition utilizing the same. Particularly, the present invention relates to synthesis of PPE copolymers with thermosetting properties and cross-linking ability and their resin compositions as well.
2. Description of the Related Art
PPE resins have good electric properties because their dissipation factor (Df) is only about 0.007 and dielectric constant (Dk) is as low as about 2.4xcx9c2.5. Furthermore, they also have high glass transition temperature (Tg), about 210xc2x0 C., and low water absorption, about 0.5%, and are good at acid and base resistance.
PPE as a thermoplastic resin, however, has very poor heat and solvent resistance. These shortcomings must be solved before PPE can be seriously considered as a material for laminate application. To date, the most effective way to solve these shortcomings has been made by transferring the thermoplastic PPE to thermosetting PPE.
Such transformation has been made as indicated in European Patent No. 382312. This patent discloses that the xe2x80x94CH3 side group on PPE is first lithiated by n-butyllithium (n-BuLi) and then reacted with allyl halide (CH2xe2x95x90CHCH2X; Xxe2x95x90Cl, Br, I) to form xe2x80x94CH2CH2CHxe2x95x90CH2. Hence a thermosetting PPE is obtained (hereafter referred to as APPE).
European Patent No. 382312 also shows that the curing reactions of APPE, peroxide and triallyl isocyanurate (TAIC) are affected only at high temperatures, 250xc2x0 C. or higher. This temperature range is too high for the common laminating process in industry. Thus, it is necessary to lower the laminating temperature to under 200xc2x0 C. before a thermosetting PPE can be practically used as a laminate.
Therefore, an object of the present invention is to solve the above-mentioned problems and to provide a method of transferring the original thermoplastic PPE to thermosetting PPE derivatives with better heat and solvent resistance for the laminate application.
Another object of the present invention is to provide thermosetting PPE derivatives with curing temperatures lower than 200xc2x0 C. This temperature capability is adequate to the common industrial laminating process.
A further object of the present invention is to provide a resin composition comprising modified PPE copolymer with low cross-linking temperature and self-cross-linking ability for laminate.
The present invention provides PPE copolymers having a dialkenylamide group, wherein the alkenyl group is C2-C10 linear alkenyl group, with the following formula (V) 
wherein
x, y and z each represent mole percentage of each repeating unit, where x is from 1 to 80%, y is from 1 to 10% and z is from 1 to 40%, provided that the sum of x, y and z is 100%,
n is 0 or an integer from 1 to 10,
R1 represents H, or C1-C10 linear or branched alkyl group,
R2 represents H, C1-C10 linear or branched alkyl group, or C2-C10 linear or branched alkenyl group, and
R3 represents H, or C2-C10 linear or branched alkenyl group.
A specific example of the PPE copolymer is where R1 is H, R2 is an allyl group, and R3 is H, or R1 is H, R2 is an isopropyl group, and R3 is H.
The process for preparing the above-mentioned PPE copolymer of the formula (V) involves admixing monomer (a), monomer (b) and monomer (c) in an organic solvent in the presence of an alkali, a copper(I) catalyst and oxygen, wherein
monomer (a): having a dialkenylamide group, wherein the alkenyl group is C2-C10 linear alkenyl group, the monomer (a) represented by the following formula (II) 
wherein the monomer (a) is synthesized by admixing and heating dihydrocoumarine and a component represented by the following formula (I) in another organic solvent, 
monomer (b): 2,6-dimethylphenol (2,6-DMP) represented by the following formula (III) 
monomer (c): represented by the following formula (IV) 
wherein
R1 represents H or C1-C10 linear or branched alkyl group, and
R2 represents H, C1-C10 linear or branched alkyl group, or C2-C10 linear or branched alkenyl group.
The present invention provides another PPE copolymer having a dialkenylamine group, wherein the alkenyl group is C2-C10 linear alkenyl group, with the following formula (VII) 
wherein
x, y and z each represent mole percentage of each repeating unit, where x is from 1 to 80%, y is from 1 to 10% and z is from 1 to 40%, provided that the sum of x, y and z is 100%,
n is 0 or an integer from 1 to 10,
R1 represents H, or C1-C10 linear or branched alkyl group,
R2 represents H, C1-C10 linear or branched alkyl group, or C2-C10 linear or branched alkenyl group, and
R3 represents H, or C2-C10 linear or branched alkenyl group.
A specific example of the PPE copolymer is where R1 is H, R2 is allyl group, and R3 is H, or R1 is H, R2 is an isopropyl group, and R3 is H.
The process for preparing the above-mentioned PPE copolymer of the formula (VII) includes admixing monomer (d), monomer (b) and monomer (c) in an organic solvent in the presence of an alkali, a copper(I) catalyst and oxygen, wherein
monomer (d): having a dialkenylamine group, wherein the alkenyl group is C2-C10 linear alkenyl group, the monomer (d) represented by the following formula (VI) 
monomer (b): 2,6-dimethylphenol (2,6-DMP) represented by the following formula (III) 
monomer (c): represented by the following formula (IV) 
wherein
R1 represents H or C1-C10 linear or branched alkyl group, and
R2 represents H, C1-C10 linear or branched alkyl group, or C2-C10 linear or branched alkenyl group.
For preparing the PPE copolymers with the formula (V) or (VII), the copper(I) catalyst can be copper(I) oxide (Cu2O) or copper(I) halide. A specific example of the copper(I) halide is Copper(I) Chloride (CuCl) or Copper(I) bromide (CuBr).
The preferred alkali is pyridine or tertiary amine, such as triethylamine.
The preferred organic solvent used to prepare the PPE copolymers is toluene or xylene.
A specific example of the monomer (c) is 2-isopropylphenol and 2-allyl-6-methylphenol.
The PPE copolymers of formula (V) and (VII) have thermosetting property, low cross-linking temperature (less than 200xc2x0 C.), and self-cross-linking ability due to double bonds in side chain.
Furthermore, because 2,6-DMP and the component of formula (II) having a dialkenylamide group or the component of formula (VI) having a dialkenylamine group are copolymerized with the present of the monomer of formula (IV), PPE copolymers have good solvent resistance and good solubility in specific solvents. According to these advantages, the PPE copolymers of formula (V) and (VII) can be applied to laminate. A detailed description of resin compositions having the PPE copolymers of formula (V) and (VII) is given.
A resin composition of the present invention comprises:
a) PPE copolymer with the formula (V) or (VII);
b) a free radical initiator present in an amount ranging from 0.5 to 95% by weight of the resin composition.
The free radical initiator used in the resin composition of the present invention is 2,5-dimethyl-2,5-di-tert-butylperoxy-hexane (DHBP), di-tert-butylperoxide (DTBP), di-cumylperoxide (DCP), or benzoylperoxide (BPO).
The above-mentioned resin composition further comprises a hardener present in an amount ranging from 5 to 95% by weight of the resin composition. The hardener can be triallyl isocyanurate (TAIC) or triallyl cyanurate (TAC).